Compounds of the type ##STR3## wherein R.sub.1 and R.sub.2 are lower alkyl are useful intermediates in the synthesis of pesticides such as herbicides containing an alkylsulfonylphenyl group. Prior art discloses production of one of these compounds, namely 2-chloro-4-methylsulfonyltoluene, by chlorination of 4-methylsulfonyltoluene with chlorine gas in the presence of antimony trichloride catalyst. We found that this process was not entirely satisfactory due to the difficulties in handling chlorine gas and the formation of undesirable impurities, which we determined resulted partially from dichlorination of the ring.
Standard methods of eliminating the undesirable impurities were not satisfactory. We have now discovered that the undesired dichlorinated and other impurities which are formed when using chlorine gas as a chlorinating agent can be greatly reduced by instead employing sulfuryl chloride as a chlorinating agent.